A Wet Moon

The Moon’s status as a “dry” rock in space has long been questioned. Competing theories abound as to the source of the H20 in the lunar soil, including delivery of water to the Moon by comets.

This week, Tartèse et al announced in Geology that new analyses of lunar soil samples demonstrates that basalts from the Moon’s mantle contain hydrogen from water indigenous to Earth.

According to the authors, their work is “challenging the paradigm of a "dry" Moon, and arguing that some portions of the lunar interior are as wet as some regions of the Earth’s mantle.”

The Moon’s origin is believed to be the Earth itself, which gave rise to the Moon when a Mars-sized object impacted our planet around 4.5 billion years ago. The Earth’s mantle is known to be partially water. These latest finding raise the odds that the Moon may have a partly-aqueous core today. These results promise that at some time in the past there was water in the Moon’s mantle, inherited from an ancestral proto-Earth, which rose to the surface in magma, and became trapped in crystals called apatites.

How much water remains, and how it can be accessed to support human habitation, will be a subject of ongoing study.

The paper, “Apatites in lunar KREEP basalts: The missing link to understanding the H isotope systematics of the Moon,” was published in the journal Geology under lead author Romain Tartèse.

This video from NASA Goddard shows how NASA’s Lunar Reconnaissance Orbiter (LRO) is helping scientists understand where water is likely to exist on the south pole of the Moon. Credit: NASA Goddard on YouTube

Studying the composition of the Moon and its relationship to the Earth can help astrobiologists understand how the Earth-Moon system formed and evolved. This is important in determining whether or not the Moon played a role in shaping the habitability of our planet.